Spectrophotometric Characterization of Diazacrown Ethers Having Two Carbodithioate Groups

Abstract

The separation and determination of metal ions has been one of the most important topics in analytical chemistry. Developing highly functional chelating agents has been a great concern of many analytical chemists. Investigations for developing new types of chelating agents have produced many highly functional chelating agents having high selectivity and/or sensitivity. [1][2][3][4][5][6] Nowadays, the concepts of chelating agent design have been expanded for not only coordination bonding, but also molecular recognition by a host-guest interaction. [7][8][9][10][11][12][13][14][15] The establishment of molecular recognition was achieved along with the development of inclusion compounds, such as crown compounds, calixarenes, and cyclams. The attractive properties of inclusion compounds have encouraged their vigorous development by analytical chemists. Analytical investigations have proved their potential in analytical chemistry. [13][14][15][16][17][18][19][20] For example, a modification of crown ethers, i.e. the introduction of a side chain into a crown ring, has already been investigated for improving crown-ring selectivity and stimulating new chromoionophore development. introduced bulky groups as "block" subunits into crown compounds to improve their recognition ability for alkali metal ion or ammonium ion as ionophores of ion-selective electrodes. Takagi et al.7-9 combined a crown ether and a chromophore to synthesize a chromoionophore for alkali-metal ions or alkaline earth-metal ions.Our attempted description in this paper introduces a new concept to the design of a chelating agent. We directly combined a diazacrown ring and chelating groups in one molecule, and tried to produce some new functions from it. The direct combination of both functional groups might cause some interaction between them, which might produce new functions. For this purpose, we synthesized two new chelating agents of azacrown compounds, as illustrated in Scheme 1. We believed that our concept of active interaction between a diazacrown ring and functional groups is quite different from studies involving modifications of crown ethers which have so far been investigated.In our previous work, 21 we found that the UV-VIS absorption spectra of the Ni(II) chelates of diammonium 1,4,10, 13-tetraoxa-7,16-diazacycrooctadecane-N,N′-bis(carbodithioate) (DA18CC) and the composition ratio of the Pb(II) chelate of DA18CC were changed by the addition of alkali-metal salts or alkaline earth-metal salts. We deduced that any changes in the absorption spectra and composition ratio were due to an alteration of the steric orientation of two carbodithioate groups along with a conformation change through the coordination of an alkali metal ion into diazacrown ring of DA18CC. This paper systematically considers the spectrophotometric properties of heavy-metal chelates of DA18CC and diammonium 1,4,10-trioxa-7,13-diazacycropentadecane-N,N′-bis(carbodithioate) (DA15CC) in the presence of an alkali-metal ion or an alkaline earth-metal ion. It also discusses th...

Organic chemosensors with crown-ether groups (review)

“…The fairly simple system 1a,b is capable of combining with the ions of heavy and transition metals and leads to corresponding changes in the ultraviolet part of the spectrum: During the formation of crown ether complexes with cations (Ni 2+ , Pd 2+ , Co 2+ , Pb 2+ ) a new absorption band appears in the region of 320 nm [16]. The sensor 2 acts in a similar way but with respect to sodium and potassium ions [17].…”

Simultaneous detection of [metal(ii)–tpen]2+as kinetically inert cationic complexes using pre-capillary derivatization electrophoresis: an application to biological samples

“…Uehara et al reported some examples of interaction between the silica surface and metal complexes. [14][15][16] TPEN complexes with first-row transition metal ions (Fe 2+ , Cu 2+ , Zn 2+ , Ni 2+ , Co 2+ and Mn 2+ ) and heavy metal ions (Pb 2+ , Cd 2+ and Hg 2+ ) were detected, providing sharp peaks at pH 7-10 with high concentrations of the carrier buffer (y100 mM). However, the peaks of the complexes of alkaline earth metal ions (Ca 2+ and Mg 2+ ), and triply charged cations (Al 3+ , Fe 3+ and Co 3+ ) were not clearly observed on the CE run.…”